I can tell you from personal experience in 300uM thick medial PFC brain
slices that in layer V soley the application of bicuculline produces
very odd network behaviour. While I didn't work in current clamp, so I
can't answer in regards to spiking. In Voltage clamp, large scale
GABA-A antagonist produce HUGE, unclampable spontaneous
depolarizations.
Completely off the screen. Lord knows what would have happened if I was
in current clamp, but it certainly would have been a big burst of some
kind.
If you're trying to isolate excitation, consider intra-cellular Cl-
channel inhibitor.